1. Field of Invention
This invention relates to method and apparatus for the storage, retrieval, and loading of units of data storage medium, and particularly to method and apparatus for the storage, retrieval, and loading of cartridges of data storage medium, such as magnetic tape.
2. Prior Art and Other Considerations
Automated tape libraries were developed to expedite the selection and loading of magnetic tape reels. One such type of automated tape library resembles an elongate rectangular chamber. Racks of tape reels are provided at selected locations along the interiors of the opposing elongated walls. An interior track runs the length of the chamber between the parallel racks. A reel retrieval/loading device is mounted on a carriage that travels along the track, and is translatable along two rectangular axes in addition to the third axis of the track. The retrieval/loading device is automatically controlled to locate and engage a selected reel in a Cartesian coordinate system, and then transports the selected reel to a target on one of a plurality of tape drives. The tape drives are located along the exterior wall of the chamber at windows provided for access to the drives. The retrieval/loading device automatically mounts the selected reel on the target tape drive.
Another prior art configuration for a storage library features a cylindrical chamber, with storage racks provided along the interior of the circular wall and a plurality of peripheral devices located along the exterior at windows. The retrieval/loading device is positioned in the center of the room, is operated in a cylindrical coordinate fashion.
Magnetic tape cartridges have recently become popular as a unit of storage medium, particularly 8 mm magnetic tape cartridges (as used herein, the term "cartridge" also refers to magnetic tape cassettes). Advantageously, magnetic tape cartridges facilitate economic and compact storage of data.
Copending U.S. Pat. Nos. 4,984,106 and 4,972,277, respectively entitled CARTRIDGE LIBRARY SYSTEM AND METHOD OF OPERATION THEREOF and CARTRIDGE TRANSPORT ASSEMBLY AND METHOD OF OPERATION THEREOF, both filed on 10 Nov. 1989 and commonly assigned herewith, are incorporated herein by reference as disclosing a library system for handling magnetic tape cartridges. The automated magnetic tape cartridge library system of these patent applications includes a cabinet housing a plurality of tape drives and a plurality of racks wherein magnetic tape cartridges are stored. A cartridge transport assembly serves to retrieve a cartridge from a rack and to load the cartridge into a target tape drive. Movement of the cartridge transport assembly along X, Y, and Z rectangular coordinates axes is effected by X, Y, Z and displacement systems.
The cartridge transport assembly described above includes a pair of engagement fingers which engage a selected cartridge upon contact with the cartridge. In an engagement mode, engagement fingers are configured and oriented to engage changer grip notches provided on opposite edges of a standard 8 mm magnetic tape cartridge such that, upon engagement, the cartridge is locked between the fingers without the need of further locking mechanisms.
The cartridge transport assembly described above also includes means for detecting when a cartridge is positioned to be loaded (either into a target drive or into a storage rack). In particular, when a cartridge is positioned for loading, abutment of the cartridge with the drive or rack forces the cartridge flush against the cartridge transport assembly and depresses a plunger of the cartridge transport assembly. When depression of the plunger is detected, a solenoid carried on the cartridge transport assembly operates via linkage means to retract the engagement fingers out of the cartridge changer grip notches. The cartridge is thus released or loaded into the awaiting target drive or target rack.
Portions of the linkage means of the cartridge transport assembly dually function as ram elements for closing a tape drive door once a cartridge is loaded into a target tape drive. In this regard, after a cartridge is loaded into a target drive, the cartridge transport assembly retreats from the target drive is displaced to a side thereof. The cartridge transport assembly is then moved with respect to the X and Z axes to provide the ram elements with components of motion suitable for closing the pivotal door of the tape drive.
While other types of automated libraries have utilized reading or scanning devices such as bar code readers to read indicia on the tapes or discs stored in the library, a suitable indicia system has heretofore not been to be realized for the library system for handling magnetic tape cartridges described in the preceding paragraphs.
Moreover, whenever a door of an automated library system is opened, there is a possibility that one or more devices stored in the library may have been manually removed or placed in another location in the library. Alternatively, there is the possibility that additional devices may have been introduced into the library. In either event, the library must somehow again inventory itself lest incorrect tapes or cartridges be retrieved and read during subsequent operations.
Accordingly, it is an object of the present invention to provide a cartridge library system and method of operation thereof having reading capabilities.
An advantage of the present invention is the provision of strategically located reader apparatus for reading indicia on cartridges stored in an automated cartridge library.
Another advantage of the present invention is the provision of method and apparatus for taking inventory of a cartridge library system.
A further advantage of the present invention is the provision of a cartridge library system including cartridge racks that have detectable indicia strategically located thereon.